autofs4: deadlock during create

[linux-2.6-omap-h63xx.git] / fs / autofs4 / root.c

diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 2d4c8a3e604e776a8a5fe680d5e974c729770dd0..45ff3d63b758bd09feea0162cc0a0cbeca0473ad 100644 (file)
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -587,19 +587,20 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
        unhashed = autofs4_lookup_unhashed(sbi, dentry->d_parent, &dentry->d_name);
        if (!unhashed) {
                /*
-                * Mark the dentry incomplete, but add it. This is needed so
-                * that the VFS layer knows about the dentry, and we can count
-                * on catching any lookups through the revalidate.
-                *
-                * Let all the hard work be done by the revalidate function that
-                * needs to be able to do this anyway..
-                *
-                * We need to do this before we release the directory semaphore.
+                * Mark the dentry incomplete but don't hash it. We do this
+                * to serialize our inode creation operations (symlink and
+                * mkdir) which prevents deadlock during the callback to
+                * the daemon. Subsequent user space lookups for the same
+                * dentry are placed on the wait queue while the daemon
+                * itself is allowed passage unresticted so the create
+                * operation itself can then hash the dentry. Finally,
+                * we check for the hashed dentry and return the newly
+                * hashed dentry.
                 */
                dentry->d_op = &autofs4_root_dentry_operations;
 
                dentry->d_fsdata = NULL;
-               d_add(dentry, NULL);
+               d_instantiate(dentry, NULL);
        } else {
                struct autofs_info *ino = autofs4_dentry_ino(unhashed);
                DPRINTK("rehash %p with %p", dentry, unhashed);
@@ -607,15 +608,17 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
                 * If we are racing with expire the request might not
                 * be quite complete but the directory has been removed
                 * so it must have been successful, so just wait for it.
+                * We need to ensure the AUTOFS_INF_EXPIRING flag is clear
+                * before continuing as revalidate may fail when calling
+                * try_to_fill_dentry (returning EAGAIN) if we don't.
                 */
-               if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
+               while (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
                        DPRINTK("wait for incomplete expire %p name=%.*s",
                                unhashed, unhashed->d_name.len,
                                unhashed->d_name.name);
                        autofs4_wait(sbi, unhashed, NFY_NONE);
                        DPRINTK("request completed");
                }
-               d_rehash(unhashed);
                dentry = unhashed;
        }
 
@@ -658,7 +661,7 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
         * for all system calls, but it should be OK for the operations
         * we permit from an autofs.
         */
-       if (dentry->d_inode && d_unhashed(dentry)) {
+       if (!oz_mode && d_unhashed(dentry)) {
                /*
                 * A user space application can (and has done in the past)
                 * remove and re-create this directory during the callback.
@@ -716,7 +719,7 @@ static int autofs4_dir_symlink(struct inode *dir,
        strcpy(cp, symname);
 
        inode = autofs4_get_inode(dir->i_sb, ino);
-       d_instantiate(dentry, inode);
+       d_add(dentry, inode);
 
        if (dir == dir->i_sb->s_root->d_inode)
                dentry->d_op = &autofs4_root_dentry_operations;
@@ -844,7 +847,7 @@ static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
                return -ENOSPC;
 
        inode = autofs4_get_inode(dir->i_sb, ino);
-       d_instantiate(dentry, inode);
+       d_add(dentry, inode);
 
        if (dir == dir->i_sb->s_root->d_inode)
                dentry->d_op = &autofs4_root_dentry_operations;